Table Of Contents

Support for Multiple Registrars on SIP Trunks

The Support for Multiple Registrars on SIP Trunks on a Cisco Unified Border Element, on Cisco IOS SIP TDM Gateways, and on a Cisco Unified Communications Manager Express feature allows configuration of multiple registrars on Session Initiation Protocol (SIP) trunks, each simultaneously registered using its respective authentication instance. Beginning with Cisco IOS XE Release 3.1S, support for this feature is expanded to include the Cisco ASR 1000 Series Router. This feature allows a redundant registrar for each of the SIP trunks, which provides SIP trunk redundancy across multiple service providers.

Prerequisites

Cisco Unified Border Element

•Cisco IOS Release 15.0(1)XA or a later release must be installed and running on your Cisco Unified Border Element.

Cisco Unified Border Element (Enterprise)

•Cisco IOS XE Release 3.1S or a later release must be installed and running on your Cisco ASR 1000 Series Router.

Restrictions for Support for Multiple Registrars on SIP Trunks

The Support for Multiple Registrars on SIP trunks feature has the following restrictions:

•Old and new forms of the registrar command are mutually exclusive: the registrar can be configured in either primary/secondary mode or multiple registrar mode—not both.

•Dynamic Host Configuration Protocol (DHCP) support is not available with multiple registrars (available for primary/secondary mode only).

•Only one authentication configuration per username can be configured at any one time.

•A maximum of six registrars can be configured at any given time.

•A maximum of 12 different realms can be configured for each endpoint.

•You cannot restrict the registration of specific endpoints with specific registrars—once a new registrar is configured, all endpoints will begin registering to the new registrar.

•You cannot remove multiple configurations of credentials simultaneously—only one credential can be removed at a time.